Purpose: :
Cone photoreceptors encode light intensity, but the fidelitywith which they transmit this information to ~10 distinct typesof bipolar cells is unknown. One hypothesis is that the sameinformation is available to all bipolar cell types, and thisinformation is relayed to the inner retina. Against this view,we observed that the 3 main types of Off bipolar cells in theground squirrel (b2, b3, and b7) made significantly differentnumbers of contacts with each cone (from 1.7 to 7). The differencesin contact number suggest that the reliability of transmissioncould differ. To resolve this, we measured synaptic transmissionof information from cones to the three types of Off bipolarcells.

Conclusions: :
Different Off bipolar cell types carry information from thecone synapse at different rates. We are currently measuringcell density to verify that each class, as a whole, transmitsa different amount of information. Our results suggest thatthe three main types of bipolar cells initiate three basic informationpathways: the b3 cell initiates a high spatial resolution, low-noise"sustained" pathway; the b7 cell initiates a low-SNR, "sluggish"pathway; and, the b2 initiates a low spatial resolution, high-noise,"brisk" pathway.